Fetal testing for chromosomal abnormalities is often performed on cells obtained using amniocentesis, or alternatively, Chorionic Villus Sampling (CVS). Amniocentesis is a procedure used to retrieve fetal cells from the fluid that surrounds the fetus. This relatively invasive procedure is performed after the 12th week of pregnancy. There is about 0.5% increased risk of miscarriage following amniocentesis. CVS is relatively less invasive, and can be performed as early as 10 weeks from conception. There is about 1% increased risk of miscarriage following CVS.
At least some fetal cell types such as platelets, trophoplasts, erythrocytes and leucocytes have been shown to cross the placenta and circulate in maternal blood (Douglas et al., Am. J. Obstet. Gynec. 78, 960-973, 1959; Schroder, J. Med. Genet. 12, 230-242, 1975). Maternal blood represents a non-invasive source of fetal cell types, however the isolation of fetal cells from maternal blood is hampered by the scarcity of such fetal cells in the maternal circulation, as well as the lack of a marker that identifies all fetal cells, rather than merely a sub-population. A pan-fetal cell-specific antibody is not available.